LOOKING TO SWAP BLUE GALAXY S3 ON O2 FOR IPHONE 4S O2 !

HI I HAVE A BLUE SAMSUNG GALAXY S3 APPROX 3 MONTHS OLD ON O2 NETWORK. IM LOOKING FOR A SWAP FOR AN IPHONE 4S. MUST BE IN VERY GOOD CONDITION. MY PHONE HAS HAD SCREEN PROTECTOR AND CASE FROM DAY 1 SO IT IS IN PERFECT CONDITION. THANKS FOR LOOKING